for i in range(5):
    n=int(input(f"请输入第{i+1}门成绩:"))
    print(n)
avg=n/5
print(avg)
if avg>=90:
    return "A"
elif avg>=80 and avg<90:
    return "B"
elif avg>=70 and avg<80:
    return "C"
elif avg>=60 and avg<70:
    return "D"
else:
    return "F"
level=add()
print(level)